Engineered nanomaterials are being used or are being proposed for use in a large number of commercial products. Because of their highly diverse physical and chemical characteristics, and their small size, concerns have been raised regarding their potential to cause harm to human health or the environment. One important class of ENMs are quantum dots (Qdots) which are luminescent semiconductor nanocrystals composed of heavy metal cores (e.g. CdSe, CdTe, HgTe) with cap and coating structures that vary greatly, depending upon the characteristics required for various applications. Certain characteristics are known to be determinants for the interaction of nanoparticles with cells and tissues, including shape, size, hydrophobicity, and surface charge. Because of the highly variable nature of these and other engineered nanomaterials, it will be nonetheless difficult to predict their toxicity. Modern advances in genomics, epigenetics and bioinformatics, and the availability of multiple strains of inbred mice with well characterized polymorphisms and regulatory sequences have made it possible to map and predict toxicity pathways for many toxic substances including nanomaterials. The research proposed herein will utilize in vitro and in vivo models of airway exposure to aerosolized quantum dot nanoparticles to 1) define the physical and chemical characteristics that govern their absorption, distribution, metabolism, excretion and toxicity;2) using multiple inbred strains of mice, map toxicity pathways associated with these characteristics;and 3) incorporate the information that is obtained from these in vitro and in vivo models into a risk assessment paradigm that will be used to predict nanomaterial toxicity to humans. Such information will not only define which physical and chemical characteristics are important for the adverse biological effects of quantum dots, but will also simultaneously advance the fields of nanomaterial toxicology and functional epigenomics. These advances can then be used in safe design and manufacturing of nanomaterials so as to maximize their utility for many applications.